Die casting of component having integral seal

ABSTRACT

A method of die casting a component having an integral seal includes defining a first portion of a die cavity of a die to include an open cell structure. A second portion of the die is defined without the open cell structure. Molten metal is injected into the die cavity, and the molten metal is solidified within the die cavity to form the component having the integral seal.

BACKGROUND

This disclosure generally relates to die casting, and more particularlyto die casting components with integral seals.

Gas turbine engines generally include a compressor section, a combustorsection, and a turbine section circumferentially disposed about anengine centerline axis. At least the compressor section and the turbinesection include alternating rows of rotating rotor blades and staticstator vanes. As airflow is communicated through the gas turbine engine,the rotor blades increase the velocity of the oncoming airflow. Thestator vanes convert the velocity into pressure and prepare the airflowfor the next set of rotor blades.

Gas turbine engine components can be manufactured in a number of waysincluding machining operations, forging operations or castingoperations. Gas turbine engine components are often manufactured in aninvestment casting process. Investment casting involves pouring moltenmetal into a ceramic shell having a cavity in the shape of the componentto be cast. An abradable seal, such as a honeycomb seal, can be brazedonto the gas path side of a gas turbine engine component to improve theseal between the gas turbine engine component and any surroundingcomponents.

SUMMARY

A method of die casting a component having an integral seal includesdefining a first portion of a die cavity of a die to include an opencell structure. A second portion of the die is defined without the opencell structure. Molten metal is injected into the die cavity, and themolten metal is solidified within the die cavity to form the componenthaving the integral seal.

In another exemplary embodiment, a die casting machine includes a diecomprised of a plurality of die elements that define a die cavity, ashot tube in fluid communication with the die cavity, and a shot tubeplunger moveable within the shot tube. The die cavity includes a firstportion having an open cell structure and a second portion without theopen cell structure. The shot tube plunger is moveable within the shottube to communicate a molten metal into the die cavity to die cast acomponent having an integral seal.

The various features and advantages of this disclosure will becomeapparent to those skilled in the art from the following detaileddescription. The drawings that accompany the detailed description can bebriefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a simplified cross-sectional view of a standard gasturbine engine.

FIG. 2 illustrates a cross-sectional view of a portion of the gasturbine engine depicted in FIG. 1.

FIG. 3 illustrates an example die casting system.

FIG. 4 illustrates an example die for use with a die casting system.

FIG. 5 illustrates an insert having an open cell structure that can beused with the die of FIG. 4.

FIG. 6 illustrates another example die for use with the die castingsystem of FIG. 3.

FIG. 7 illustrates a component having an integral seal that can be castusing the die of FIG. 4 or FIG. 6.

DETAILED DESCRIPTION

FIG. 1 illustrates a gas turbine engine 10, such as a turbofan gasturbine engine, that is circumferentially disposed about an enginecenterline (or axial centerline axis) 12. The gas turbine engine 10includes a fan section 14, a compressor section 15 having a low pressurecompressor 16 and a high pressure compressor 18, a combustor 20, and aturbine section 21 including a high pressure turbine 22 and a lowpressure turbine 24. This disclosure can also extend to engines withouta fan, and with more or fewer sections.

As is known, air is compressed in the low pressure compressor 16 and thehigh pressure compressor 18, is mixed with fuel and burned in thecombustor 20, and is expanded in the high pressure turbine 22 and thelow pressure turbine 24. Rotor assemblies 26 rotate in response to theexpansion, driving the low pressure and high pressure compressors 16, 18and the fan section 14. The compressor section 15 and the turbinesection 21 may include alternating rows of rotating rotor blades 28 andstatic stator vanes 30.

It should be understood that this view is included simply to provide abasic understanding of the sections of a gas turbine engine 10 and notto limit the disclosure. This disclosure extends to all types of gasturbine engines 10 for all types of applications.

FIG. 2 illustrates a portion of the gas turbine engine 10. In thisexample, the portion depicted is the high pressure turbine 22 of the gasturbine engine 10. However, this disclosure is not limited toapplications within the high pressure turbine 22, and could extend toother sections of a gas turbine engine 10, including but not limited to,the low pressure turbine 24 and the compressor section 15. In addition,selected features of the high pressure turbine 22 are shown enlarged inorder to illustrated specific details and are not shown to the scalethey would be in operation.

The high pressure turbine section 22 includes a rotor assembly 26 havinga plurality of rotor blades 28 (one depicted) extending outwardly fromthe circumference of the rotor assembly 26. The rotor blades 28 extendbetween a rim 27 of the rotor assembly 26 and a blade tip 40.

An outer casing 42 extends circumferentially about the high pressureturbine section 22 at a position radially outward from the rotor blades28. The outer casing 42 includes a plurality of blade outer air seals(BOAS) 44 positioned between the blade tips 40 of the rotor blades 28and the outer casing 42. The BOAS 44 includes an integral seal 46, suchas an abradable seal, that interacts with the rotor blades 28 tomitigate gas leakage. During operation, the rotor blades 28 rotate aboutthe engine centerline axis 12 and at least partially wear away a portionof the integral seal 46 to seal and mitigate gas leakage around thecomponents within the high pressure turbine section 22. In theillustrated example, a portion 45 has been partially worn away by therotor blade 28.

FIG. 3 illustrates a die casting system 48 for die casting a component,such as the BOAS 44 or other seals. However, this disclosure is notlimited to the die casting of BOAS, and it should be understood that anyaeronautical or non-aeronautical component can be die cast with anintegral seal according to the example methodologies of this disclosure.

The die casting system 48 includes a reusable die 50 having a pluralityof die elements 52, 54 that function to cast the component. Although twodie elements 52, 54 are depicted in FIG. 3, it should be understood thatthe die 50 could include more or fewer die elements, as well as otherparts and configurations.

The die 50 is assembled by positioning the die elements 52, 54 togetherand holding the die elements 52, 54 at a desired position via amechanism 56. The mechanism 56 could include a clamping mechanism ofappropriate hydraulic, pneumatic, electromechanical and/or otherconfigurations. The mechanism 56 also separates the die elements 52, 54subsequent to casting.

The die elements 52, 54 define internal surfaces that cooperate todefine a die cavity 58. A shot tube 53 is in fluid communication withthe die cavity 58 via one or more ports 60 located in the die element52, the die element 54 or both. A shot tube plunger 62 is receivedwithin the shot tube 53 and is moveable between a retracted and injectedposition (in the direction of arrow A) within the shot tube 53 by amechanism 64. The mechanism 64 could include a hydraulic assembly orother suitable mechanism, including, but not limited to, pneumatic,electromechanical or any combination thereof.

The shot tube 53 is positioned to receive a molten metal from a meltingunit 66, such as a crucible, for example. The melting unit 66 mayutilize any known technique for melting an ingot of metallic material toprepare molten metal for delivery to the shot tube 53, including but notlimited to, vacuum induction melting, electron beam melting andinduction scald melting. The molten metal is melted by the melting unit66 at a location that is separate from the shot tube 53 and the die 50.In this example, the melting unit 66 is positioned in relatively closeproximity to the shot tube 53 to reduce the required transfer distancebetween the molten metal and the shot tube 53.

Example molten metals capable of being used to die cast a componentinclude, but are not limited to, nickel base super alloys, cobaltalloys, titanium alloys, high temperature aluminum alloys, copper basedalloys, iron alloys, molybdenum, tungsten, niobium, or other refractorymetals. This disclosure is not limited to use of the disclosed alloys,and it should be understood that any high melting temperature materialmay be utilized to die cast a component. As used herein, the term “highmelting temperature material” is intended to include materials having amelting temperature of approximately 1500° F./815° C. and higher.

The molten metal is transferred from the melting unit 66 to the shottube 53 in a known manner, such as pouring the molten metal into a pourhole 55 in the shot tube 53, for example. A sufficient amount of moltenmetal is communicated into the shot tube 53 to fill the die cavity 58.The shot tube plunger 62 is actuated to inject the molten metal underpressure from the shot tube 53 into the die cavity 58 to cast thecomponent. Although the casting of a single component is depicted, thedie casting system 48 could be configured to cast multiple components ina single shot.

Although not necessary, at least a portion of the example die castingsystem 48 can be positioned within a vacuum chamber 70 that includes avacuum source 72. A vacuum is applied in the vacuum chamber 70 by thevacuum source 72 to render a vacuum die casting process. The vacuumchamber 70 provides a non-reactive environment for the die castingsystem 48 that reduces reaction, contamination or other conditions thatcould detrimentally affect the quality of the cast component, such asexcess porosity of the cast component that occurs as a result ofexposure to oxygen. In one example, the vacuum chamber 70 is maintainedat a pressure between 1×10⁻³ Torr and 1×10⁻⁴ Torr, although otherpressures are contemplated. The actual pressure of the vacuum chamber 70will vary based upon the type of component being cast, among otherconditions and factors. In the illustrated example, each of the meltingunit 66, the shot tube 53 and the die 50 are positioned with the vacuumchamber 70 during the die casting process such that the melting,injecting and solidifying of the metal are all performed under vacuum.In another example, the vacuum chamber 34 is backfilled with an inertgas, such as Argon, for example.

The example die casting system 48 depicted in FIG. 3 is illustrativeonly and could include more or less sections, parts and/or components.This disclosure extends to all forms of die casting, including but notlimited to, horizontal, inclined or vertical die casting systems.

FIG. 4 illustrates an example die 150 for use with a die casting system,such as the die casting system 48 depicted in FIG. 3. In thisdisclosure, like reference numerals signify like features, and referencenumerals identified in multiples of 100 signify slightly modifiedfeatures. Moreover, select features of one example embodiment may becombined with selected features of other example embodiments. The die150 may be used to die cast a component, such as a BOAS having anintegral seal, or any other component.

The die 150 includes a die cavity 158 that is defined by a plurality ofdie elements 152, 154. The die cavity 158 includes a first portion 80and a second portion 82. In the illustrated example, the first portion80 and the second portion 82 are openings within the die 150. Althoughthe example die cavity 158 is depicted as including two portions, itshould be understood that more or less portions may define the diecavity 158. Also, the size of shape of the first portion 80 and thesecond portion 82 will vary depending upon design specific parametersincluding, but not limited to, the type of component being cast.

In this example, the first portion 80 of the die cavity 158 isconfigured to receive an insert 84. The insert 84 is generally sized andshaped similar to the first portion 80. In the example embodiment, theinsert 84 is a honeycomb seal made of a Nickel Alloy or other highmelting temperature material that includes an open cell structure 85that defines walls 87 having openings 88 therebetween, such as diamondshaped openings (See FIG. 5). Other inserts having different structuresare contemplated as being within the scope of this disclosure. Theinsert 84 is positioned within the first portion 80 of the die cavity158 either manually or automatically, such as with a robot, for example.

The second portion 82 of the die cavity 158 does not include the opencell structure. Therefore, the second portion 82 represents a void oropening within the die 150 that is sized and shaped to correspond to thecomponent being cast. The second portion 82 of the die cavity 158receives molten metal M from a die casting system, such as the diecasting system 48 detailed above. Molten metal M is injected into thedie cavity 158 via the shot tube 53 and the shot tube plunger 62 and issolidified within the die cavity 158. The molten metal M locally bondswith the insert 84 at an interface I during solidification of the moltenmetal M to cast a component having an integral seal. In other words, thecomponent is die cast against the insert 84, thereby overcasting thecomponent (the portion solidified in the second portion 82) having anintegral seal (the locally bonded insert 84 located in the first portion80) in a single operation.

FIG. 6 illustrates another exemplary die 250 that may be used with a diecasting system, such as the die casting system 48 depicted above. Thedie 250 is utilized to die cast a component having an integral seal,such as a BOAS having a honeycomb seal, for example. Other aeronauticaland non-aeronautical components may also be cast using the die 250.

The die 250 includes a die cavity 258 defined by a plurality of dieelements 252, 254. The die cavity 258 defines a first portion 280 and asecond portion 282, although more or fewer portions may be definedwithin the die cavity 258. Also, the size of shape of the first portion280 and the second portion 282 will vary depending upon design specificparameters including, but not limited to, the type of component beingcast.

In this example, the first portion 280 of the die cavity 258 ispre-defined with an open cell structure 285 that corresponds to adesired structure of an integral seal. That is, the first portion 280 ofthe die cavity 258 is formed with design features, such as a honeycomb,open cell structure, that are automatically form corresponding featureswithin a cast component once molten metal is injected into the diecavity 258, i.e., no inserts are required. The open cell structure 285may be formed within the first portion 280 of the die cavity 258 in anyknown manner. The first portion 280 defines the integral seal on thecast component.

The second portion 282 is defined without an open cell structure.Therefore, the second portion 282 represents a void or opening withinthe die 250 that is sized and shaped to correspond to the componentbeing cast. The second portion 282 of the die cavity 258 is made largerby a distance X to define the first portion 280, which forms theintegral seal portion of the cast component. That is, enlarging thesecond portion 282 of the die cavity 258 by a distance X allows theintegral seal to be die cast as a feature of the component during thedie casting process.

Subsequent to melting, molten metal M is injected into the die cavity258 and is communicated to both the first portion 280 and the secondportion 282 of the die cavity 258. The molten metal solidifies withinthe die cavity 258 to form a component having an integral seal. Becausethe first portion 280 is defined with an open cell structure, oncesolidified, the molten metal forms a component having an integral sealwith a desired structure, such as a honeycomb seal structure, forexample.

FIG. 7 illustrates a component 29 that may be die cast using the exampledies 150, 250 described above. The component 29 includes a body portion31 and an integral seal 33. Each of the body portion 31 and the integralseal 33 may be made from nickel based super alloys, cobalt alloys,titanium alloys, high temperature aluminum alloys, copper based alloys,iron alloys, molybdenum, tungsten, niobium, other refractory metals, orany combination of such materials. Any high melting temperature materialmay be utilized to die cast the component 29. In this example, thecomponent 29 is a seal having an integral seal 33 with an open cellstructure 35, although other components may also be cast using theexample dies 150, 250, including but limited to BOAS, inner air sealsand 1-2 seals. The integral seal 33 is a honeycomb abradeable seal suchthat contact with a rotor blade partially wears away the integral seal33.

The foregoing description shall be interpreted as illustrative and notin any limiting sense. A worker of ordinary skill in the art having thebenefit of this disclosure would recognize that certain modificationscould come within the scope of the disclosure. For these reasons, thefollowing claims should be studied to determine the true scope andcontent of this disclosure.

1. A method of die casting a component with an integral seal, comprisingthe step of: (a) defining a first portion of a die cavity of a die toinclude an open cell structure; (b) defining a second portion of the diecavity without the open cell structure; (c) injecting molten metal intothe die cavity; (d) solidifying the molten metal within the die cavityto form the component with the integral seal.
 2. The method as recitedin claim 1, wherein said step (a) includes: positioning an insert thatdefines the open cell structure within the first portion of the diecavity.
 3. The method as recited in claim 2, wherein said step (d)includes: locally bonding the insert with the component to provide thecomponent with the integral seal.
 4. The method as recited in claim 2,wherein the insert is a honeycomb abradeable seal.
 5. (canceled) 6.(canceled)
 7. The method as recited in claim 1, wherein said step (c)includes: melting an ingot of material to prepare the molten metal;communicating the molten metal into a shot tube; and injecting themolten metal into the die cavity with a shot tube plunger.
 8. The methodas recited in claim 1, wherein the component is a seal having anintegral honeycomb abradeable seal.
 9. The method as recited in claim 1,comprising the step of: (e) positioning the die within a vacuum chamber.10. The method as recited in claim 1, wherein the first portion and thesecond portion of the die cavity are openings within the die, and thefirst portion defines the integral seal and the second portion definesthe component. 11-15. (canceled)
 16. The method as recited in claim 1,wherein the open cell structure establishes walls having openingsbetween the walls.
 17. The method as recited in claim 1, wherein thecomponent and the integral seal are formed together within the diecavity.
 18. The method as recited in claim 1, wherein said step (a)includes: positioning an insert that is a honeycomb seal made of anickel alloy within the first portion of the die cavity.
 19. A method ofdie casting a component with an integral seal, comprising: positioningan insert within a portion of a die cavity of a die, wherein the insertdefines an open cell structure having walls with openings extendingbetween the walls; injecting molten metal into the die cavity; andsolidifying the molten metal within the die cavity to overcast thecomponent against the insert to establish the integral seal on thecomponent.